This invention relates to the valve art and more particularly to ball valves.
The invention is particularly applicable to a new high pressure ball valve and will be described with particular reference thereto. However, it will become readily apparent to those skilled in the art that the invention is capable of broader applications and could be adapted to use in other types and styles of valves.
Typically, ball valve constructions in commercial use employ annular seats or seat rings formed of a plastic material. For large ball valves or for ball valves specifically designed for high pressure use (above approximately 2500 psi), the ball member is usually trunnion supported with these valve seats or seat rings having the capability of floating and being pressure activated to seal against the ball. However, in such large size and high pressure ball valves, some steps must be taken to limit the amount of fluid pressure which will act on the seats to prevent the imposition of destructively high compressive stresses thereagainst.
Therefore, and in order to eliminate compressive stresses of a magnitude which may severly damage or destroy the seats or seat rings, it has become necessary to employ pressure controlled seats in conjunction with a bearing or trunnion supported ball. While some valve constructions of this type are known in the art, the specific constructions and operational details thereof have not satisfactorily met the needs of industry. In particular, some prior designs have involved very sophisticated and/or cumbersome structures which cause production difficulties and add to the valve costs. Other prior designs of this type are for special or limited applications and are not adapted to general high pressure shut-off applications. Still other prior high pressure valves have involved constructions which, after relatively short periods of use, would not properly function and allowed destructive forces to be imparted to the valve seats.
It has, therefore, been desired to develop a high pressure ball valve which would overcome the foregoing problems. Such a design would desirably utilize a trunnion mounted ball with plastic seats, be adaptable to use in a wide range of applications or environments and be effective for a large number of valve cycles. The present invention contemplates a new and improved high pressure ball valve construction which is deemed to meet all of the foregoing needs and others.